WO2011095719A1

WO2011095719A1 - Voltage drop control method and voltage drop limiting device, recording medium for said method, and vehicle with said limiting device integrated thereinto

Info

Publication number: WO2011095719A1
Application number: PCT/FR2011/050077
Authority: WO
Inventors: Erwan Monnier; Lionel Dolmaire; Serge Da Cruz Pereira; Bernard Boucly
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2010-02-03
Filing date: 2011-01-17
Publication date: 2011-08-11
Also published as: FR2955989A1; FR2955989B1

Abstract

The invention relates to a method for controlling a power switch that is connected in series between a terminal of an electric motor and a terminal of a battery supplying power to said motor. Said method comprises a phase (50) for limiting the strength of the power supply current to the motor by controlling the power switch so as to systematically keep the voltage in the battery terminals above a predetermined threshold. Said method is characterized in that, during said limiting phase, the strength of the power supply current is mainly limited by controlling the power switch in linear mode.

Description

CONTROL METHOD AND VOLTAGE DROPOUT LIMITER, RECORDING MEDIUM FOR THIS METHOD AND VEHICLE INCORPORATING THIS

LIMITER

[Oooi] The present invention claims the priority of the French application 1050755 filed February 3, 2010 whose content (text, drawings and claims) is here incorporated by reference.

The invention relates to a method for controlling a power switch connected in series between a terminal of an electric motor and a terminal of a battery supplying this motor. The invention also relates to:

• a voltage drop limiter at the battery terminals,

An information recording medium for implementing this method, and

• a vehicle equipped with this voltage drop limiter. [0oo3] Known methods for controlling a power switch include a phase of limiting the intensity of the power supply current of the motor by controlling the power switch so as to systematically maintain the voltage across the battery terminals. above a predetermined threshold. [ooo4] A power switch is a switch that can be traversed by a high current for several tens of seconds without being damaged. High current means here a current greater than 3 A and, preferably, greater than or equal to 1000 A. To achieve this performance, a power switch is often composed of several elementary power transistors connected in parallel with each other. to others between a common input electrode and a common output electrode of the power switch. These common input and output electrodes are for example known by the term "drain" and "source" when the power transistors are transistors. field effect. These same input and output electrodes of the high current are called "collector" and "emitter" when the power transistors are bipolar transistors.

[ooo5] Each power switch also has a common control electrode. The control electrodes of the different power transistors forming the power switch are connected to this common control electrode so as to simultaneously control the switching of all the elementary transistors. This common control electrode is called a "gate" when the power transistor is a field effect transistor. It is also called "base" when the power transistor is a bipolar transistor.

[ooo6] In the patent application EP 1 041 278, the power switch is controlled pulse width modulation (PWM), better known by the acronym PWM (Pulse Width Modulation). This control makes it possible to limit the intensity of the supply current of the electric motor, in particular when it is started.

[ooo7] By varying a duty cycle a, it is possible to limit the amplitude of the peak of current intensity related to the starting of the electric motor. By limiting the amplitude of the peak intensity, it also limits the voltage drop across the battery that powers the starter.

[ooo8] However, the use of pulse width modulation makes the process more difficult and more complex to implement. For example, the implementation of a pulse width modulation creates significant electromagnetic disturbances and makes it necessary to connect a freewheeling diode across the power switch.

[Ooo9] The invention aims to remedy at least one of these disadvantages. It therefore relates to a method of controlling the power switch in which, during this limitation phase, the essential of the limitation of the intensity of the supply current is obtained by driving the power switch in steady state. linear. In linear mode, the power switch behaves as a resistor whose value varies depending on the voltage applied to the control electrode. The intensity of the current flowing through the power switch is a function of this resistance and therefore of the voltage applied to the control electrode of the power switch. Generally, in linear mode, the intensity of the current flowing through the power switch between its input and output electrodes is proportional to the voltage applied to the control electrode. Thus, the control of the power switch in a linear mode makes it possible to vary this resistance and therefore to limit the intensity of the current without making it switch repetitively between passing and non-conducting states, that is to say without cutting out food.

[ooi i] There are also two other operating modes for a power switch: the saturated mode and the blocked mode. In the saturated regime, the power switch has a minimum equivalent resistance. This regime is obtained when the voltage on the control electrode exceeds a certain threshold. The intensity of the current flowing through the switch depends essentially on the characteristics of the load supplied via this transistor.

In steady state, the power switch does not let any current. Thus, in blocked mode, the switch is off or open. The control method above is simpler to implement because it does not require the power supply current of the electric motor by means of the power switch. Since there is no current hashing, the electromagnetic disturbances caused by such current switching are reduced. In addition, the fact of not chopping the current also simplifies the architecture. Indeed, for example, it is not necessary to add a freewheel diode across the power switch as in the case where the current is chopped by the switch.

[ooi4] Embodiments of this method may include one or more of the following features: During the limitation phase, the method comprises measuring the voltage at the terminals of the battery and controlling the power switch in linear mode according to the measured voltage so as to automatically adjust the intensity of the current flowing through. the power switch according to the measured voltage;

During the limitation phase, the power switch is controlled in linear mode as a function of the difference between the measured voltage and the predetermined threshold in order to control the measured voltage on this predetermined threshold;

• the method comprises measuring the intensity of the current flowing through the power switch and the automatic passage of the power switch in blocked mode as soon as the measured intensity exceeds a predetermined threshold;

The power switch comprises at least one field effect transistor and the driving of the power switch in linear mode consists in applying to the gate of this field effect transistor a voltage constructed so that a voltage V _G s between the gate and the source of this transistor is maintained greater than a threshold V _T H beyond which the transistor leads and the voltage V _D s between the drain and the source is kept strictly less than V _G s - V _TH .

[Ooi 5] These embodiments of the method further have the following advantages:

• Controlling the power switch according to the voltage measured at the terminals of the battery makes it possible to automatically adapt the control of the power switch to variations in the characteristics of the battery or the electric motor; · Controlling the power switch to control the measured voltage to a predetermined threshold maximizes the usable electrical power to start the electric motor without falling below this threshold voltage at the terminals of the battery; • Measure the intensity of the current through the power switch to provide additional protection against failures of the electric motor such as a short circuit.

The invention also relates to an information recording medium containing instructions for the implementation of the above method of controlling the power switch, when these instructions are executed by an electronic computer.

The invention also relates to a voltage drop limiter at the terminals of a battery during the start-up of this electric motor, a limiter comprising:

A power switch connected in series between a terminal of the battery and a terminal of the electric motor, and

A control unit able to execute a phase of limiting the intensity of the motor supply current by controlling the power switch so as to systematically maintain the voltage across the battery above a predetermined threshold .

[Ooi 8] During the limitation phase, the control unit is able to obtain the essential of the limitation of the intensity of the supply current by driving the power switch in linear mode. The embodiments of this limiter may comprise the following characteristic:

The power switch comprises at least one field effect transistor and, preferably, at least one MOSFET transistor.

Finally, the invention also relates to a vehicle incorporating this voltage drop limiter.

The embodiments of this vehicle may comprise the following characteristic: The vehicle comprises an electric starter of a thermal engine of the vehicle connected to the battery by means of the voltage drop limiter.

The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and with reference to the drawings in which:

FIG. 1 is a schematic illustration of a vehicle equipped with a voltage drop limiter, and

FIG. 2 is a flowchart of a method of controlling a power switch of the voltage drop limiter of FIG. 1.

In the following description, the features and functions well known to those skilled in the art are not described in detail.

[0024] Figure 1 shows a vehicle 2 such as a motor vehicle. For example, the vehicle 2 is a car. This vehicle 2 comprises an internal combustion engine 4 to drive in rotation of the drive wheels 6, 8.

The vehicle 2 also comprises a battery 10 to which are connected different electrical charges 12 via an edge network 14. [0027] Typically, the battery 10 is an electrochemical battery. The battery 10 is equipped with a terminal 15A connected to the vehicle ground and a terminal 15B connected to the different electrical loads powered from this battery.

The voltage between the terminals 15A, 15B of the battery is noted V _ba tt-

A starter 16 is also connected to the onboard network 14 to be supplied with electric current from the battery 10. The starter 16 is an electric motor adapted to rotate the motor shaft 4 to start it. The starter 16 is associated with a switch 18. The switch 18 controls the movement of a pinion between:

A position engaged with a starter ring of the engine 4, and

• a position disengaged from the starter ring. The switch 18 also controls the supply of the starter 16 by moving a movable contact 20. For this, the contactor comprises for example a plunger. Such a contactor is described in more detail in patent application FR 2 749 451.

The switch 18 is controlled by a control device 19. The starter 16 is connected to the terminal 15B of the battery 10 via a limiter 24 of voltage drop. This limiter 24 limits the voltage drop V _b a _tt caused by starting the starter 16. In fact, when the starter 16 starts, this causes a high inrush current. This current draw, in the absence of the limiter 24, can cause a significant drop in the voltage on the onboard network 14 may cause the stop operation of some of the loads 12.

For this purpose, the limiter 24 comprises a power switch 26 connected in series between the terminal 15B and a power supply terminal of the motor 16. This power switch is for example a field effect transistor such as a MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor).

The drain of this switch is directly connected to the terminal 15B. The source of this switch is connected to the power supply terminal of the starter 16.

The grid is connected to a control unit 28. The control unit 28 is also connected to sensors 30 and 34. The sensor 30 measures a magnitude representative of the voltage V _batt - The sensor 34 measures the intensity of the current flowing through the switch 26.

The unit 28 controls the switch 26 to prevent the voltage V _ba tt from falling below a predetermined threshold Si when starting the starter 16. This threshold Si is chosen sufficiently high to allow the loads 12 to continue to function normally when starting the starter 16. Here, the unit 28 is able to implement the method described with reference to FIG. is typically performed from a programmable electronic computer capable of executing instructions recorded on an information recording medium. For this purpose, the unit 28 is connected to a memory 36 in which are recorded instructions for the implementation of the method of FIG. 2. The parameters such as the value of the threshold Si and the value of a threshold S ₂ necessary to the operation of the unit 28 are also recorded in this memory 36. The limiter 24 also comprises a unit 38 for management and control. This unit 38 allows the limiter 24 to communicate with different devices external to the limiter 24. For example, the signals exchanged between the limiter 24 and these external devices may be the following:

The request for driving the starter 16, a deactivation command for the limiter 24,

Receiving a calibration command that makes it possible, for example, to modify the thresholds S ₁ and S ₂ , and

• the indication of a fault, for example, detected by the limiter 24.

In Figure 1, the external devices are schematically represented by a block 40. These external devices can therefore affect the operation of the limiter 24 by sending information or commands to the unit 38.

The unit 38 is connected to the unit 28.

The operation of the limiter 24 will now be described with reference to the method of Figure 2. [0042] The start of the starter 16 causes a sudden current call which causes a drop in the voltage V _ba tt- In response at this start-up, there is proceeded to a phase 50 of time limited in time during which the unit 28 is authorized to drive, if necessary, the power switch 26 in linear mode to limit the intensity of the supply current of the starter 1 6. During the phase 50, this control of the switch 26 in linear regime becomes necessary when the voltage V _ba tt is about to fall below a threshold Yes . More specifically, during phase 50, the unit 28 drives the switch 26 in linear mode so that it acts as a variable resistor.

During the control of the switch 26 in the linear mode, the switch 26 is maintained by passing that is to say that the unit 28 applies a voltage on its gate so as to maintain the voltage V _GS between the gate and the source greater than a threshold V _TH - Threshold V _TH is the threshold of the voltage V _GS beyond which the switch becomes conductive. At the same time, the voltage applied by the unit 28 on the gate maintains the voltage V _D s between the drain and the source strictly less than the voltage VQ _S - _JH - In these conditions, the switch 26 operates in linear mode that is to say as a variable resistor whose value is fixed by the gate voltage V _G applied by the unit 28. Thus, the intensity of the current flowing through this switch is a function of the gate voltage.

In addition, when the switch 26 is controlled in linear mode, the unit 28 builds the gate voltage V _G so as to slave the voltage V _ba tt so that it is greater than or equal to the threshold value. Yes . For example, here, when driving in linear mode, the voltage V _ba tt is slaved to the threshold Si. For this purpose, the unit 28 applies on the gate of the switch 26 a voltage V _G constructed as a function of the difference between the voltage measured by the sensor 30 and the threshold Si. More specifically, the gate voltage V _G applied is constructed to reduce the difference between the voltage measured by the sensor 30 and the threshold Si.

For example, to reduce the intensity of the current flowing through the switch 26, the gate voltage V _G is decreased. Conversely, to increase the intensity of the current, the gate voltage is increased.

During phase 50, the current demand caused by the start can decrease so that the voltage V _ba tt naturally rises above the threshold Si. In response thereto, the unit 28 also increases the gate voltage V _G to increase the intensity of the current flowing through the switch 26. After some times, the gate voltage has increased enough that the switch 26 out of the linear regime and enters saturated mode.

When the predetermined duration of phase 50 has elapsed, it ends and a phase 52 begins. During the phase 52 the switch 26 is controlled in saturated mode and the control in linear mode is prohibited. When the switch 26 is in saturated mode, the intensity of the current flowing through it is a function of the electrical charges connected between these terminals, that is to say here in particular the electrical characteristics of the starter 1 6. On the other hand, in saturated mode the voltage applied to the gate alone does not allow the intensity of the current flowing through the switch to be regulated as in linear mode.

To control the switch 26 in saturated mode, the unit 28 applies a gate voltage so that the voltage V _G s is greater than the threshold V _T H and the voltage V _D s is greater than V _G s - V _T H- The operation of the switch 26 in saturated mode during phase 52 ensures that the engine 1 6 has the maximum available electrical power.

For example, the phase 52 is completed when the engine 1 6 is stopped. We then return to phase 50 which will be triggered the next time the starter 1 6 is started.

In parallel with the phases 50 and 52, a step 54 of detecting a failure is executed continuously. In step 54, the unit 28 compares the intensity of the current measured by the sensor 34 with the threshold S ₂ . As long as the intensity of the current remains below the threshold S ₂ , then no failure is detected. Otherwise, the unit 28 detects a failure and then immediately blocks the switch 26 so as to disconnect the starter 1 6 of the battery 14. The unit 28 can also transmit this information to external devices via of unit 38.

Many other embodiments are possible. For example, the sensor 30 may be integrated in the limiter 24 or, on the contrary, remote. For example, the sensor 30 may be deported to be closer to the terminals of the battery 10. Alternatively, the current measurement may be omitted. In this case, the sensor 34 is omitted and the step 54 also.

The unit 38 may also be omitted in another embodiment. In this case, the limiter 24 operates completely autonomously and the unit 28 is simplified.

The switch 26 can be made from other transistors as MOSFET transistors. For example, the switch 26 is made from at least one field effect transistor such as a JFET (Junction Feild Effect Transistor) transistor. The switch 26 can also be made from transistors other than field effect such as a bipolar transistor.

Alternatively, the switch 18 and its control device may be omitted.

The limiter 24 may be applied in other contexts than that described with reference to FIG. 1. In particular, the limiter 24 can be used to limit the voltage drop caused by the start of any electric charge supplied by the battery 10. The limiter 24 can also be used to limit the voltage drops caused by the setting running an electric motor that is not necessarily embedded in a motor vehicle.

The starter 16 may also be an alternator starter.

Claims

1. A method of controlling a power switch connected in series between a terminal of an electric motor and a terminal of a battery supplying this motor, this method comprising a phase (50) for limiting the intensity of the current. supplying the motor by controlling the power switch so as to systematically maintain the voltage across the battery above a predetermined threshold, characterized in that, during this limitation phase, the essential of the limitation of the intensity of the supply current is obtained by driving the power switch in linear mode.

2. Method according to claim 1, wherein, during the limitation phase (50), the method comprises measuring the voltage across the battery and controlling the power switch linearly depending on the voltage measured so as to automatically adjust the intensity of the current flowing through the power switch according to the measured voltage.

3. Method according to claim 2, wherein, during the limitation phase (50), the power switch is controlled in linear mode as a function of the difference between the measured voltage and the predetermined threshold to control the voltage measured on it. predetermined threshold.

4. Method according to any one of the preceding claims, wherein the method comprises measuring (54) the intensity of the current flowing through the power switch and the automatic passage of the power switch in blocked mode as soon as the measured intensity exceeds a predetermined threshold.

5. Method according to any one of the preceding claims, wherein the power switch comprises at least one field effect transistor and the control of the power switch in linear mode consists in applying to the gate of this transistor to field effect a voltage constructed so that a voltage V _G s between the gate and the source of this transistor is maintained greater than a threshold VJH beyond which the transistor leads and the voltage V _D s between the drain and the source is kept strictly below V _G s - V _T H-

6. Support (36) for recording information, characterized in that it comprises instructions for the implementation of a method according to any one of the preceding claims, when these instructions are executed by an electronic calculator .

7. A voltage drop limiter at the terminals of a battery supplying an electric motor when the electric motor is started, is a limiter comprising:

A power switch (26) connected in series between a terminal of the battery and a terminal of the electric motor, and

A control unit (28) capable of executing a phase of limiting the intensity of the motor supply current by controlling the power switch so as to systematically maintain the voltage at the terminals of the battery above a predetermined threshold, characterized in that, during the limitation phase, the control unit (28) is able to obtain the essential of the limitation of the intensity of the supply current by driving the power switch into linear regime.

8. Limiter according to claim 7, wherein the power switch (26) comprises at least one field effect transistor and, preferably, at least one MOSFET transistor.

9. Vehicle, characterized in that it comprises a limiter (24) of voltage drop according to any one of claims 7 or 8.

10. Vehicle according to claim 10, wherein the vehicle comprises an electric starter (16) of a thermal engine of the vehicle connected to the battery via the limiter (24) voltage drop.